1. Field of the Invention
This invention relates in general to a single-ended forward frequency converter including a transformer and having a demagnetization means.
2. Description of the Related Art
A single-ended forward frequency converter is disclosed in U.S. Pat. No. 4,415,959. The transformer in this patent is intentionally propvided with a leakage inductance which forms a resonant circuit together with the storage capacitor. The electronic switch is opened at the end of a half period of the sinusoidal input current and is then in a zero current condition. In the case of the control of the electronic switch with a control circuit, the off-times during which the switch are opened circuited are varied with a constant on time. A free-wheeling diode with a following LC filter section is connected in parallel following the storage capacitor. Such free-wheeling diode becomes current conducting during every energy transmission cycle as soon as the storage capacitor is substantially discharged. The demagnetization of the transformer after the end of the on-time is accomplished with the assistance of the electronic switch or by using a suitable network.
U.S. Pat. No. 4,441,146 discloses a demagnetization means for a forward frequency converter that comprises a series conduit of a capacitor and an electronic switch with a control circuit. The demagnetization means in this patent is relatively expensive.
See also European patent application No. 0 223 504 and the article appearing in Mullard Technical Communications, Vol. 13, No. 127, Pages 258-279, July 1975 entitled "Television Switched-Mode Power Supply Using the TDA 2640 by L. M. White.